1. Field of the Invention
The present invention relates to wirelines inserted down a string of drill pipe. More particularly, the present invention relates to an apparatus for guiding wireline within the derrick of an oil rig, during wireline operations, which can be used with a top drive system, and further includes an upper packer portion allowing packing off of the wireline in the event of a blow out, and for accommodating an overshot for latching onto a wireline tool retrieved from down hole.
2. General Background
In an oil rig operation, it is often necessary that wireline operations be conducted to undertake certain tasks down hole during drilling. In such operations, a wireline unit is disposed adjacent to the rig floor which would drive a steel cable, or wireline, around a pulley wheel mounted at the top of the oil derrick, with the wireline traveling downwardly through the oil derrick towards the rig floor, and ultimately through the pack off assembly which is connected to the bottom of the circulating head which is made into the bottom end of the drill pipe. The wireline is utilized to control the drill pipe for directional drilling, for example with the the use of a bent sub, the bent sub having a drilling bit mounted to its outer end for drilling. The wireline is often used for other tasks such as surveying downhole, or the like. Often times a wireline utilizes a tool at the end in order to retrieve items which have been lost downhole so that drilling may be resumed after the items are retrieved.
Often times during wireline operations, the wireline, particularly in use with a top drive system, may cause damage to the top drive system as the wire is run through the assembly from the pulley, in order to feed the wireline down the hole. In other types of operations, even when a top drive assembly system is not utilized, the wireline being fed straight down the hole may necessarily cause fraying or even severing of the wireline due to friction or the like on the bell portion of the assembly.
The present inventor is the named patentee in U.S. Pat. No. 4,469,171 entitled "Wireline Guiding Apparatus", which was issued on Sept. 4, 1984. This assembly, included an elongated stationary arm having parallel trusses, attached at a 45.degree. angle to a collar in a pack off assembly and extending upwardly and outwardly, an elongated swivel arm, swivelly attached at its lower end to the uppermost portion of the stationary arm, and extending upwardly and inwardly at about 45.degree. angle. There was included a first pulley wheel mounted between trusses and support by an upper portion of the swivel arm. The pulley receiving the wireline and guided it vertically downward into the pack off assembly. There was further included a bumper connected to the upper portion of the swivel arm for preventing any contact between the traveling block and the wireline. Further, there were a plurality of support plates mounted between the truss at a 45.degree. angle in relation to the truss. A third movable arm having two parallel trusses, and having a second pulley wheel rotatable mounted between the truss for receiving and guiding the wire line, the third arm further having a plurality of reinforcement plates attached between the trusses, and provided with a sleeve to cover a diagonal opening made in one of the third arms. This combination allowed the feeding of a wireline at a position not in aligned with the drill pipe, and enabling it to angle toward the hole, around the second lower pulley wheel, which would enable it to be fed directly into the pipe. This angling of the wireline down into the hole via the apparatus as disclosed in the '171 patent, avoided any contact with the assembly above the drill pipe into which the wireline was being fed.
However, of all the shortcomings of the invention as disclosed and claimed in the '171 patent, was the fact that the wireline that was being fed through the plate sub mounted to the upper portion of the drill pipe allowed the drill pipe to be open to atmosphere, and should a blow out occur, the drill pipe was not secure since the wireline apparatus was in place. Secondly, the bumper on the lower portion of the assembly, although providing a means to prevent the damage to the wireline assembly that was connected to the drill pipe, when a tool was retrieved downhole, did not eliminate the problem of the tool making contact with the assembly, and perhaps severing the line which would in effect cause the tool to be dropped down into the hole which has to be then retrieved.